Tire having an improved bead structure

ABSTRACT

A heavy load vehicle tire includes a bead structure having two reinforcing layers adjacent to the inner side of the carcass turned up ply and a chafer layer including reinforcing elements. The reinforcing layers are preferably made of steel cords including preformed filaments, the cords being inclined at angles between +10° to +35° and −10° to −35° with respect to the radial plane of the tire.

The present invention relates to a tire having, an improved beadstructure.

More in particular, the present invention relates to a tire, preferablyto a heavy load vehicle tire, comprising an improved bead structure.

As it is known, a tire usually comprises a pair of bead structurescomprising at least one bead core and at least one bead filler; acarcass structure of a substantially toroidal shape, comprising at leastone carcass ply usually including a plurality of reinforcing elements,extending between the bead structures, said carcass ply having its endportions turned up around said bead core; a belt structure applied in aradially external position with respect to said carcass structure; atread band radially superimposed on said belt structure; a pair ofsidewalls applied laterally on opposite sides with respect to saidcarcass structure.

It is known that, both bead structures and sidewalls, are subjected to alarge bending deformation during the running of the tire under loading,in particular under the action of a large loading. In particular,because of said bending deformation, the generation of strain or theconcentration of stress at the radially outer end of the carcass plyturned up end portions and at neighborhood thereof, may occur. As aresult, there is a problem that a crack may occur at the radially outerend of the carcass ply turned up end portions which, because ofrepetitiveness of said bending deformation, may cause bead structurefailure by the growth of such a crack. Consequently, the bead structuredurability is lowered.

Attempts to solve the abovementioned drawbacks have been made in theart.

For example, U.S. Pat. No. 4,953,605 relates to a radial tire for heavyloads, comprising: a pair of bead cores; a carcass the ends of which areturned up around the bead cores to form a carcass main part and acarcass turned up part on the axially inside and the outside of the beadcore, respectively; a metallic cord reinforcing layer turned up aroundthe bead core to form (a) an outside part extending along the axiallyoutside of the carcass turned up part and (b) an inside part extendingalong the axially inside of the carcass main part; an outsidereinforcing layer of organic fiber cords disposed axially outside theoutside part of the metallic cord reinforcing layer; an insidereinforcing layer of organic fiber cords disposed on the axially insideof the carcass main part; a bead apex between the carcass main part andthe turned up part extending radially outwardly beyond the radiallyouter end of the outside reinforcing layer; a rubber chafer disposedoutside the outside reinforcing layer; and an inner sidewall disposedbetween the outside reinforcing layer and the rubber chafer extendingradially outwardly beyond the radially outer end of the outsidereinforcing layer so as to contact with a buffer of the bead apex. Theabovementioned tire is said to have an improved reinforced structure forthe bead part which allow to improve the bead part durability undersevere service conditions.

U.S. Pat. No. 5,151,140 relates to a heavy-duty pneumatic radial tirehaving a bead portion comprising a carcass layer having its respectiveend portions turned up about a bead core from the axially inner side tothe axially outer side of the tire and at least two reinforcing layersdisposed along a portion of the carcass layer, said at least tworeinforcing layers comprising an inner reinforcing layer of steel cordshaving a layer tenacity of from 30 kg/mm of layer width to less than 80kg/mm of layer width, incorporated on the axially inner side of the beadportion, and an outer reinforcing layer of steel cords having a greaterlayer tenacity than the inner reinforcing layer and of at least 80 kg/mmof layer width, incorporated on the axially outer side of the beadportion, wherein the inner reinforcing layer extends from the axiallyinner side of the bead portion to the axially outer side of the portionand terminates at an area corresponding to the radially inner end of theouter reinforcing layer, wherein cords in the inner reinforcing layerand cords in the outer reinforcing layer are inclined in a samedirection relative to the radial direction of the tire, and wherein whenmounted on a vehicle the direction of inclination of the cords in theinner and the outer reinforcing layers is opposite the direction offorward rotation of the tire. The abovementioned tire is said to have animproved durability of the bead portion.

U.S. Pat. No. 6,079,467 relates to a heavy duty radial tire comprising atread portion, a pair of sidewall portions, a carcass ply extendingbetween the bead portions through the tread portion and sidewallportions and turned up around bead cores from the axially inside to theoutside of the tire to form a pair of turnup portions and a main portiontherebetween, a bead apex disposed between the carcass main portion andeach turnup portion of the carcass ply and extending radially outwardlyfrom the bead core, and a chafer disposed in each bead portion to definea rim contacting surface, each turnup portion extending radiallyoutwardly beyond the radially outer end of the bead apex so that theturnup portion has a parallel part which is placed adjacent to andsubstantially in parallel with the main portion, said chafer extendingradially outwardly along the axially outside of the turnup portionbeyond the radially outer end of the bead apex. The abovementioned tireis said to have an improved bead durability.

European Patent Application EP 1,502,771 relates to a pneumatic tirecomprising at least one carcass ply of steel cords, in which a wrap partwound on a bead core along its outer peripheral face is disposed in aturnup portion of the carcass ply and at least one wire chafer woundaround the bead core from a main body portion of the carcass ply towardthe turnup portion thereof in a widthwise direction is embedded in thebead portion, and a shortest distance of a start end of the wire chaferlocated at the side of the main body portion of the carcass ply asmeasured outward from a normal line drawn to an outer face of the beadportion at a first rim line position in the radial direction of the tireis located to be within a range of 15-25 mm, and a terminal end of thewire chafer located at the side of the turnup portion of the carcass plyis arranged within a range defined between a vertical line drawn from anoutermost end position of the bead core in the radial direction to theouter face of the bead portion and said normal line. The abovementionedtire is said to have an excellent bead portion durability.

The Applicant has faced the problem of providing a tire having animproved bead structure. In particular, the Applicant has faced theproblem of providing a tire, more in particular a heavy load vehicletire, wherein the generation of strain or the concentration of stress atthe radially outer end of the carcass ply turned up end portions and atneighborhood thereof, are remarkably reduced, so remarkably reducingalso the risk of a crack occurrence therein which may cause a beadstructure failure.

The Applicant has now found that it is possible to obtain a tire havingthe above characteristics by placing at least two reinforcing layersaxially inside with respect to the carcass ply turned up end portions.

According to a first aspect, the present invention relates to a tirecomprising:

-   -   a pair of bead structures, said, bead structures comprising at        least one bead core and at least one bead filler;    -   a carcass structure having a substantially toroidal shape        comprising at least one carcass ply extending between said bead        cores, the end portions of said carcass ply being turned up        around said bead cores from the axially inner side to the        axially outer side of said tire;    -   a belt structure applied in a radially external position with        respect to said carcass structure;    -   a tread band radially superimposed on said belt structure;    -   a pair of sidewalls, each sidewall being applied laterally on        opposite sides with respect to said carcass structure;    -   at least one chafer placed axially outside with respect to said        carcass ply turned up end portions;    -   at least two reinforcing layers placed axially inside with        respect to said carcass ply turned up end portions, said at        least two reinforcing layers comprising:    -   an outer reinforcing layer provided with reinforcing elements        parallel to one another and inclined with respect to a radial        direction of said tire;    -   an inner reinforcing layer, placed axially inside with respect        to said outer reinforcing layer, provided with reinforcing        elements parallel to one another and inclined with respect to        the radial direction of said tire in a direction opposite to        those of said outer reinforcing layer;        wherein the lowest radially inner end of one of said outer        reinforcing layer and said inner reinforcing layer, is placed at        a tire height (h1) which is lower than or equal to 35%,        preferably of from 10% to 30%, more preferably of from 15% to        25%, with respect to a tire height (h2) in correspondence to the        maximum tire section width (W).

For the aim of the present description and of the claims which follows,any “height” in a tire radial section is determined as the perpendiculardistance in the radial direction from the nominal rim diameter to thepoint concerned.

Said “nominal rim diameter” is determined according to ETRTO Standard.

For the aim of the present description and of the claims which follows,the term “maximum tire section width” refers to the maximum linear axialdistance between two points on the outer surface of the sidewalls, saidaxial distance being parallel to the rotation axis of the tire.

According to one preferred embodiment, the radial distance (d1) betweenthe radially inner ends of said outer reinforcing layer and said innerreinforcing layer, is higher than or equal to 4 mm, preferably of from 5mm to 8 mm.

For the aim of the present description and of the claims which follows,the term “radial distance” refers to the radial distance between twopoints, in particular to the difference between the heights of said twopoints.

According to one preferred embodiment, the radially inner end of saidouter reinforcing layer is staggered radially outward with respect tothe radially inner end of said inner reinforcing layer.

According to one preferred embodiment, the radial distance (d2) betweenthe radially outer end of said carcass ply turned up end portions andthe highest radially inner end of one of said outer reinforcing layerand said inner reinforcing layer, is higher than or equal to 8 mm,preferably of from 10 mm to 15 mm.

According to one preferred embodiment, when the radially outer end ofsaid at least one chafer is placed at a higher height with respect tothe radially outer end of said carcass ply turned up end portions, theradial distance (d3) between the lowest radially outer end of one ofsaid outer reinforcing layer and said inner reinforcing layer and theradially outer end of said at least one chafer, is higher than or equalto 4 mm, preferably of from 5 mm to 8 mm.

According to one preferred embodiment, when the radially outer end ofsaid at least one chafer is placed at a lower height with respect to theradially outer end of said carcass ply turned up end portions, theradial distance (d6) between the lowest radially outer end of one ofsaid outer reinforcing layer and said inner reinforcing layer and theradially outer end of said carcass ply turned up end portions, is higherthan or equal to 4 mm, preferably of from 5 mm to 8 mm.

According to one preferred embodiment, the radial distance (d4) betweenthe radially outer ends of said outer reinforcing layer and said innerreinforcing layer, is higher than or equal to 4 mm, preferably of from 5mm to 8 mm.

According to one preferred embodiment, the radially outer end of saidinner reinforcing layer is staggered radially outward with respect tothe radially outer end of said outer reinforcing layer.

According to one preferred embodiment, the radial distance (d5) betweenthe highest radially outer end of one of said outer reinforcing layerand said inner reinforcing layer and the radially outer end of said atleast one chafer, is lower than or equal to 35%, preferably of from 15%to 20%, with respect to a tire height (h2) in correspondence to themaximum tire section width (W).

According to one preferred embodiment, the highest radially outer end ofone of said outer reinforcing layer and said inner reinforcing layer, isplaced at a tire height (h3) which is lower than or equal to 60%,preferably of from 30% to 50%, more preferably of from 35% to 45%, withrespect to a tire height (h2) in correspondence to the maximum tiresection width (W).

According to one preferred embodiment, the reinforcing elements of saidouter reinforcing layer and said inner reinforcing layer are metalcords, preferably steel cords.

According to a further preferred embodiment, said metal cords compriseat least one elementary metal wire. Preferably, said metal cordscomprise at least one preformed elementary metal wire, while theremaining elementary metal wires forming said metal cords are of thenon-preformed type. More preferably, the elementary metal wires formingsaid metal cords are all preformed.

Preferably, said elementary metal wire has a diameter in the range offrom 0.05 mm to 0.25 mm, more preferably of from 0.10 mm to 0.20 mm.

Preferably, the preformed elementary metal wire is preformed in a plane.

Preferably, said elementary metal wire is preformed so that it assumes awave-shaped configuration so that it is substantially devoid of sharpedges and/or discontinuities in curvature along their longitudinalextension. Said feature is particularly advantageous since the absenceof said sharp edges results in a favourable increasing of the breakingload of the elementary metal wire.

Particularly preferred is a preforming according to substantiallysinusoidal undulations. Preferably, said sinusoidal undulations have awavelength of from 2.5 mm to 30 mm, and more preferably of from 5 mm to25 mm.

Preferably, said sinusoidal undulations have a wave amplitude of from0.12 mm to 1 mm. The wavelength and wave amplitude ranges referred toabove may be measured directly on the non-rubberized elementary metalwire before it is inserted into the tire or on the finished (vulcanized)tire. Advantageously, the measurement of said parameters may beperformed on the elementary metal wire by using a magnifying lens and agraduated scale (for example, a graduated ruler). In the case where afinished (or vulcanized) tire is to be analysed, it is necessary toextract the reinforcing layer from the tire and to remove therubberizing compound therefrom by using suitable solvents, for exampleby treating it with dichlorobenzene at 100° C. for at least 12 hours.

In an alternative embodiment, the elementary metal wire is not preformedin a plane but, for example, is helically preformed.

In order to obtain said preformed elementary metal wire, it is possibleto use any one of the methods known in the sector. For example, it ispossible to use toothed-wheel devices of the type illustrated in U.S.Pat. No. 5,581,990, or to use the device described in InternationalPatent Application WO 00/39385.

According to one preferred embodiment, said elementary metal wire ismade of steel.

According to one preferred embodiment, the reinforcing elements of saidouter reinforcing layer are inclined with a radial inclination angle offrom +10° to +35°, preferably of from +15° to +25°.

According to one preferred embodiment, the reinforcing elements of saidinner reinforcing layer are inclined with a radial inclination angle offrom −10° to −35°, preferably of from −15° to −25°.

With “radial inclination angle” of each reinforcing element it is meantthe smallest angle between a lying plane of the reinforcing elementperpendicular to the tire equatorial plane and a radial plane of thetire passing in correspondence of the radially inner extremity of thesame reinforcing element. This angle conventionally has a positive valuewhen the smallest angle is obtained by rotating the radial plane in theclockwise direction to overlap with the lying plane of the reinforcingelement, while it has a negative value when the above rotation is in thecounterclockwise direction.

A radial inclination angle is depicted in FIG. 7, where it isschematically shown a side view of a portion of the outer reinforcinglayer (6) and the inner reinforcing layer (7) placed on the tire in anaxial internal position with respect to a carcass ply turned up endportion (not shown in FIG. 7). The radial inclination angle is indicatedby +α and in this case it has a positive value and −α and in this casehas a negative value, while with P it is indicated the radially innerextremity of the reinforcing element of the outer reinforcing layer (6),with P′ it is indicated the radially inner extremity of the reinforcingelement of the inner reinforcing layer (7), and with R the tire radialplane passing through points P and P′.

For the aim of the present description and of the claims which follow,except in the operating examples, or where otherwise indicated, allnumbers expressing amounts, quantities, percentages, and so forth, areto be understood as being modified in all instances by the term “about”.Also, all ranges include any combination of the maximum and minimumpoints disclosed and include any intermediate ranges therein, which mayor may not be specifically enumerated herein.

Additional features and advantages of the invention will be betterapparent from the following description of some preferred embodiments ofa tire according to the present invention, which description is made, byway of non-limiting example, with reference to the attached FIG. 1-6wherein:

FIG. 1 is a view in cross-section of a portion of a tire according tothe present invention;

FIG. 2 is an enlarged view in cross-section of a bead structure of thetire of FIG. 1;

FIG. 3-6 are enlarged views in cross-section of bead structuresaccording to further embodiments according to the present invention.

For simplicity, FIG. 1 shows only a portion of the tire, the remainingportion not represented being identical and simmetrically arranged withrespect to the equatorial plane (x-x) of the tire. The tire (1)comprises at least one carcass ply (2), the opposite lateral edges ofwhich are associated with respective bead structures (3) comprising atleast one bead core (4) and at least one bead filler (5). Theassociation between the carcass ply (2) and the bead core (4) isachieved here by folding back the opposite lateral edges of the carcassply (2) around the bead core (4) so as to form the carcass ply turned upend portion (2 a) as represented in FIG. 1.

The carcass ply (2) generally consists of a plurality of reinforcingelements arranged parallel to each other and at least partially coatedwith a layer of a crosslinked elastomeric material. These reinforcingelements are usually made of steel wires stranded together, coated witha metal alloy (for example copper/zinc, zinc/manganese,zinc/molybdenum/cobalt alloys and the like) or of textile fibres, forexample rayon, nylon or polyethylene terephthalate.

The carcass ply (2) is usually of radial type, i.e. it incorporatesreinforcing elements arranged in a substantially perpendicular directionrelative to a circumferential direction. The bead core (4) is enclosedin a bead structure (3), defined along an inner circumferential edge ofthe tire (1), with which the tire engages on a rim (not represented inFIG. 1) forming part of a vehicle wheel. The space defined by eachcarcass ply turned up end portion (2 a) contains a bead filler (5)usually made of a crosslinked elastomeric material, wherein the beadcore (4) is embedded.

An outer reinforcing layer (6) provided with reinforcing elementsparallel to one another and inclined with respect to the radialdirection of the tire (1), is placed axially inside with respect to saidcarcass ply turned up end portion (2 a).

An inner reinforcing layer (7) provided with reinforcing elementsparallel to one another and inclined with respect to the radialdirection of the tire (1) in a direction opposite to those of said outerreinforcing layer (6), is placed axially inside with respect to saidouter reinforcing layer (6).

As mentioned above, the reinforcing elements of said outer reinforcinglayer and said inner reinforcing layer, are metal cords, preferablysteel cords, comprising at least one elementary metal wire. Saidelementary metal wire is preferably made of steel. In the case where thediameter of the elementary metal wire is of from 0.1 mm to 0.4 mm, thebreaking strength of a standard NT (normal tensile) steel ranges from2600 N/mm² (or 2600 MPa—MegaPascal) to 3200 N/mm², the breaking strengthof a HT (High Tensile) steel ranges from 3000 N/mm² to 3600 N/mm², thebreaking strength of a SHT (Super High Tensile) steel ranges from 3300N/mm² to 3900 N/mm², the breaking strength of a UHT (Ultra High Tensile)steel ranges from 3600 N/mm² to 4200 N/mm². Said breaking strengthvalues depend in particular on the quantity of carbon contained in thesteel.

Generally, said elementary metal wire is provided with a brass coating(Cu of from 60% to 75% by weight, Zn of from 40% to 25% by weight),having a thickness of from 0.10 μm to 0.50 μm. Said coating ensuresbetter adhesion of the elementary metal wire to the elastomeric materialand provides for protection against corrosion of the metal, both duringproduction of the tire and during use thereof. Should it be necessary toensure a greater degree of protection against corrosion, said elementarymetal wire may be advantageously provided with an anti-corrosive coatingother than brass, able to ensure a greater corrosion resistance, suchas, for example, a coating based on zinc, zinc/manganese (ZnMn) alloys,zinc/cobalt (ZnCo) alloys or zinc/cobalt/manganese (ZnCoMn) alloys.

Preferably, the reinforcing elements of said outer (6) and inner (7)reinforcing layers are obtained by using cords having a structure of thetype n×D, where n is the number of elementary metal wires forming thecord and D is the diameter of each elementary metal wire. Preferably nranges from 2 to 6.

Preferably, the stranding pitch of said cords ranges from 2.5 mm to 25mm, more preferably from 6 mm to 18 mm. Preferred cord constructionsare, for example: 2× (i.e. two elementary metal wires twisted together),3×, 4×, 5×, 2+1 (i.e. one strand of two elementary metal wires and onestrand of one elementary metal wire, said two strands being twistedtogether), 2+2, 1+4, +5.

Preferably, the density of the reinforcing elements in said outer (6)and inner (7) reinforcing layers is of from 40 cords/dm to 160 cords/dm,more preferably of from 80 cords/dm to 120 cords/dm.

Preferably, the thickness of said outer (6) and inner (7) reinforcinglayers, i.e. the total thickness including the diameter of the cord andthe elastomeric material into which the cord are embedded, is of from0.6 mm to 1.5 mm, preferably from 0.8 mm to 1.2 mm.

A chafer (8) is placed axially outside with respect to said carcass plyturned up end portion (2 a).

The chafer (8) comprises a plurality of reinforcing elements which areembedded in a crosslinked elastomeric material and which are generallymade of textile materials (e.g., aramide, ryon) or metal materials(e.g., steel cord).

The chafer (8) may be located in a plurality of positions inside of thetire bead and/or sidewall. According to the embodiment shown in FIG. 1,the chafer (8) is located in a position axially outside with respect tosaid carcass ply turned up end portion (2 a).

Alternatively the chafer (8) is located in a position axially outsidewith respect to said carcass ply turned up end portion (2 a) and iswound around the bead core (4) and the bead filler (5) so as to at leastpartially envelope them (as shown in FIG. 6).

In the particular embodiment of FIG. 1, said outer reinforcing layer (6)has its radially inner end staggered radially outward with respect tothe corresponding radially inner end of said inner reinforcing layer(7).

In the particular embodiment of FIG. 1, the radially inner end of saidinner reinforcing layer (7) is placed at a tire height (h1) which islower than or equal to 35%, preferably of from 10% to 30%, morepreferably of from 15% to 25%, with respect to a tire height (h2) incorrespondence to the maximum tire section width (W).

In the particular embodiment of FIG. 1, the radial distance (d1) betweenthe radially inner end of said outer reinforcing layer (6) and theradially inner end of said inner reinforcing layer (7), is higher thanor equal to 4 mm, preferably of from 5 mm to 8 mm.

In the particular embodiment of FIG. 1, the radial distance (d2) betweenthe radially outer end of said carcass ply turned up end portion (2 a)and the radially inner end of said outer reinforcing layer (6), ishigher than or equal to 8 mm, preferably of from 10 mm to 14 mm.

In the particular embodiment of FIG. 1, the radial distance (d3) betweenthe radially outer end of said outer reinforcing layer (6) and theradially outer end of said chafer (8), is higher than or equal to 4 mm,preferably of from 5 mm to 8 mm.

In the particular embodiment of FIG. 1, the radial distance (d4) betweenthe radially outer end of said inner reinforcing layer (7) and theradially outer end of said outer reinforcing layer (6), is higher thanor equal to 4 mm, preferably of from 5 mm to 8 mm.

In the particular embodiment of FIG. 1, the radially outer end of saidinner reinforcing layer (7) is staggered radially outward with respectto the radially outer end of said outer reinforcing layer (6).

In the particular embodiment of FIG. 1, the radial distance (d5) betweenthe radially outer end of said inner reinforcing layer (7) and theradially outer end of said chafer (8), is lower than or equal to 35%,preferably of from 15% to 30%, with respect to a tire height (h2) incorrespondence to the maximum tire section width (W).

In the particular embodiment of FIG. 1, the radially outer end of saidinner reinforcing layer (7) is placed at a tire height (h3) which islower than or equal to 60%, preferably of from 30% to 50%, morepreferably of from 35% to 45%, with respect to a tire height (h2) incorrespondence to the maximum tire section width (W).

An antiabrasive strip (12) is usually placed in an axially externalposition relative to the carcass ply turned up end portion (2 a).

A belt structure (10) is applied along the circumference of the carcassply (2). In the particular embodiment of FIG. 1, the belt structure (10)comprises four belt layers (10 a), (10 b), (10 c) and (10 d), which areradially superimposed and which incorporate a plurality of reinforcingelements, typically metal cords, said reinforcing elements beingparallel to each other in each layer and intersecting with respect tothe adjacent layer, inclined preferably in a symmetrical manner withrespect to the equatorial plane (x-x) of the tire at an angle of from10° to 70°, preferably of from 12° to 40°, and coated and weldedtogether by means of a crosslinked elastomeric material. Preferably,said reinforcing elements have a density of from 30 cords/dm to 80cords/dm, preferably of from 40 cords/dm to 65 cords/dm, measured onsaid four belt layers (10 a), (10 b), (10 c) and (10 d), in acircumferential direction, close to the equatorial plane (x-x) of thetire (1).

Alternatively, the belt structure (10) may comprise a lateralreinforcing layer (not shown in FIG. 1), commonly known as “zero-degreereinforcing layer”, radially superimposed on the carcass ply (2). Saidlateral reinforcing layer generally incorporates a plurality ofreinforcing elements, typically metal cords with a breakage elongationvalue of from 3% to 10%, preferably of from 3.5% to 7%, said reinforcingelements being oriented in a substantially circumferential direction,thus forming an angle of a few degrees (i.e.)0° with respect to theequatorial plane (x-x) of the tire, and coated and welded together bymeans of a crosslinked elastomeric material. Preferably, saidreinforcing elements have a density of from 30 cords/dm to 80 cords/dm,preferably of from 40 cords/dm to 60 cords/dm, measured on said lateralreinforcing layer, in a circumferential direction, close to theequatorial plane (x-x) of the tire.

In the particular embodiment of FIG. 1, an insert (14) comprising acrosslinked elastomeric material is located at the buttress area, i.e.the area where the lateral edges of the tread band (11) is connected tothe sidewall (13). Usually, the insert (14) is interposed between thecarcass ply (2), the belt structure (10) and the sidewall (13).

A sidewall (13) is applied externally onto the carcass ply (2), thissidewall extending, in an axially external position, from the beadstructure (3) to the end of the belt structure (10).

A tread band (11), whose lateral edges are connected to the sidewall(13), is applied circumferentially in a position radially external tothe belt structure (10). Externally, the tread band (11) has a rollingsurface (11 a) designed to come into contact with the ground.Circumferential grooves (11 b) which are connected by transverse notches(not represented in FIG. 1) so as to define a tread pattern whichcomprises a plurality of blocks of various shapes and sizes distributedover the rolling surface (11 a) are generally made in this surface (11a).

In the case of tubeless tires, a rubber layer (9) generally known as aliner, which provides the necessary impermeability to the inflation airof the tire, may also be provided in an inner position relative to thecarcass ply (2).

In FIG. 1, the section width (W) which refers to the maximum linearaxial distance between two points on the outer surface of the sidewalls13, said axial distance being parallel to the rotation axis of the tire(1), is also represented.

FIG. 2′ shows an enlarged view in cross-section of a bead structureaccording to FIG. 1. For simplicity of description, the reference signshere reported have the same meanings as disclosed in the above FIG. 1.

FIG. 3 shows an enlarged view in cross-section of a further beadstructure according to the present invention. For simplicity ofdescription, the reference signs here reported have the same meanings asdisclosed in the above FIG. 1.

In the particular embodiment of FIG. 3, said outer reinforcing layer (6)has its radially inner end staggered radially inward with respect to thecorresponding radially inner end of said inner reinforcing layer (7).

In the particular embodiment of FIG. 3, the radially inner end of saidouter reinforcing layer (6), is placed at a tire height (h1) which islower than or equal to 35%, preferably of from 10% to 30%, morepreferably of from 15% to 25%, with respect to a tire height (h2) incorrespondence to the maximum tire section width (W).

In the particular embodiment of FIG. 3, the radial distance (d1) betweenthe radially inner end of said inner reinforcing layer (7) and theradially inner end of said outer reinforcing layer (6), is higher thanor equal to 4 mm, preferably of from 5 mm to 8 mm.

In the particular embodiment of FIG. 3, the radial distance (d2) betweenthe radially outer end of said carcass ply turned up end portion (2 a)and the radially inner end of said inner reinforcing layer (7), ishigher than or equal to 8 mm, preferably of from 10 mm to 14 mm.

In the particular embodiment of FIG. 3, the radial distance (d3) betweenthe radially outer end of said inner reinforcing layer (7) and theradially outer end of said chafer (8), is higher than or equal to 4 mm,preferably of from 5 mm to 8 mm.

In the particular embodiment of FIG. 3, the radial distance (d4) betweenthe radially outer end of said outer reinforcing layer (6) and theradially outer end of said inner reinforcing layer (7), is higher thanor equal to 4 mm, preferably of from 5 mm to 8 mm.

In the particular embodiment of FIG. 3, the radially outer end of saidouter reinforcing layer (6) is staggered radially outward with respectto the radially outer end of said inner reinforcing layer (7).

In the particular embodiment of FIG. 3, the radial distance (d5) betweenthe radially outer end of said outer reinforcing layer (6) and theradially outer end of said chafer (8), is lower than or equal to 35%,preferably of from 15% to 30%, with respect to a tire height (h2) incorrespondence to the maximum tire section width (W).

In the particular embodiment of FIG. 3, the radially outer end of saidouter reinforcing layer (6) is placed at a tire height (h3) which islower than or equal to 60%, preferably of from 30% to 50%, morepreferably of from 35% to 45%, with respect to a tire height (h2) incorrespondence to the maximum tire section width (W).

FIG. 4 shows an enlarged view in cross-section of a further beadstructure according to the present invention. For simplicity ofdescription, the reference signs here reported have the same meanings asdisclosed in the above FIG. 1.

In the particular embodiment of FIG. 4, said outer reinforcing layer (6)has its radially inner end staggered radially outward with respect tothe corresponding radially inner end of said inner reinforcing layer(7).

In the particular embodiment of FIG. 4, the radially inner end of saidinner reinforcing layer (7) is placed at a tire height (h1) which islower than or equal to 35%, preferably of from 10% to 30%, morepreferably of from 15% to 25%, with respect to a tire height (h2) incorrespondence to the maximum tire section width (W).

In the particular embodiment of FIG. 4, the radial distance (d1) betweenthe radially inner end of said outer reinforcing layer (6) and theradially inner end of said inner reinforcing layer (7), is higher thanor equal to 4 mm, preferably of from 5 mm to 8 mm.

In the particular embodiment of FIG. 4, the radial distance (d2) betweenthe radially outer end of said carcass ply turned up end portion (2 a)and the radially inner end of said outer reinforcing layer (6), ishigher than or equal to 8 mm, preferably of from 10 mm to 14 mm.

In the particular embodiment of FIG. 4, the radial distance (d3) betweenthe radially outer end of said inner reinforcing layer (7) and theradially outer end of said chafer (8), is higher than or equal to 4 mm,preferably of from 5 mm to 8 mm.

In the particular embodiment of FIG. 4, the radial distance (d4) betweenthe radially outer end of said outer reinforcing layer (6) and theradially outer end of said inner reinforcing layer (7), is higher thanor equal to 4 mm, preferably of from 5 mm to 8 mm.

In the particular embodiment of FIG. 4, the radially outer end of saidouter reinforcing layer (6) is staggered radially outward with respectto the radially outer end of said inner reinforcing layer (7).

In the particular embodiment of FIG. 4, the radial distance (d5) betweenthe radially outer end of said outer reinforcing layer (6) and theradially outer end of said chafer (8), is lower than or equal to 35%,preferably of from 15% to 30%, with respect to a tire height (h2) incorrespondence to the maximum tire section width (W).

In the particular embodiment of FIG. 4, the radially outer end of saidouter reinforcing layer (6) is placed at a tire height (h3) which islower than or equal to 60%, preferably of from 30% to 50%, morepreferably of from 35% to 45%, with respect to a tire height (h2) incorrespondence to the maximum tire section width (W).

FIG. 5 shows an enlarged view in cross-section of a further beadstructure according to the present invention. For simplicity ofdescription, the reference signs here reported have the same meanings asdisclosed in the above FIG. 1.

In the particular embodiment of FIG. 5, said outer reinforcing layer (6)has its radially inner end staggered radially inward with respect to thecorresponding radially inner end of said inner reinforcing layer (7).

In the particular embodiment of FIG. 5, the radially inner end of saidouter reinforcing layer (6) is placed at a tire height (h1) which islower than or equal to 35%, preferably of from 10% to 30%, morepreferably of from 15% to 25%, with respect to a tire height (h2) incorrespondence to the maximum tire section width (W).

In the particular embodiment of FIG. 5, the radial distance (d1) betweenthe radially inner end of said inner reinforcing layer (6) and theradially inner end of said outer reinforcing layer (7), is higher thanor equal to 4 mm, preferably of from 5 mm to 8 mm.

In the particular embodiment of FIG. 5, the radial distance (d2) betweenthe radially outer end of said carcass ply turned up end portion (2 a)and the radially inner end of said inner reinforcing layer (7), ishigher than or equal to 8 mm, preferably of from 10 mm to 14 mm.

In the particular embodiment of FIG. 5, the radial distance (d3) betweenthe radially outer end of said outer reinforcing layer (6) and theradially outer end of said chafer (8), is higher than or equal to 4 mm,preferably of from 5 mm to 8 mm.

In the particular embodiment of FIG. 5, the radial distance (d4) betweenthe radially outer end of said inner reinforcing layer (7) and theradially outer end of said outer reinforcing layer (6), is higher thanor equal to 4 mm, preferably of from 5 mm to 8 mm.

In the particular embodiment of FIG. 5, the radially outer end of saidouter reinforcing layer (6) is staggered radially inward with respect tothe radially outer end of said inner reinforcing layer (7).

In the particular embodiment of FIG. 5, the radial distance (d5) betweenthe radially outer end of said inner reinforcing layer (7) and theradially outer end of said chafer (8), is lower than or equal to 35%,preferably of from 15% to 30%, with respect to a tire height (h2) incorrespondence to the maximum tire section width (W).

In the particular embodiment of FIG. 5, the radially outer end of saidinner reinforcing layer (7) is placed at a tire height (h3) which islower than or equal to 60%, preferably of from 30% to 50%, morepreferably of from 35% to 45%, with respect to a tire height (h2) incorrespondence to the maximum tire section width (W).

FIG. 6 shows an enlarged view in cross-section of a further beadstructure according to the present invention. For simplicity ofdescription, the reference signs here reported have the same meanings asdisclosed in the above FIG. 1.

In the particular embodiment of FIG. 6, a chafer (8) is located in aposition axially outside with respect to said carcass ply turned up endportion (2 a) and is wound around the bead core (4) and the bead filler(5) so as to at least partially envelope them.

In the particular embodiment of FIG. 6, said outer reinforcing layer (6)has its radially inner end staggered radially outward with respect tothe corresponding radially inner end of said inner reinforcing layer(7).

In the particular embodiment of FIG. 6, the radially inner end of saidinner reinforcing layer (7) is placed at a tire height (h1) which islower than or equal to 35%, preferably of from 10% to 30%, morepreferably of from 15% to 25%, with respect to a tire height (h2) incorrespondence to the maximum tire section width (W).

In the particular embodiment of FIG. 6, the radial distance (d1) betweenthe radially inner end of said outer reinforcing layer (6) and theradially inner end of said inner reinforcing layer (7), is higher thanor equal to 4 mm, preferably of from 5 mm to 8 mm.

In the particular embodiment of FIG. 6, the radial distance (d2) betweenthe radially outer end of said chafer (8) and the radially inner end ofsaid outer reinforcing layer (6), is higher than or equal to 8 mm,preferably of from 10 mm to 14 mm.

In the particular embodiment of FIG. 6, the radial distance (d4) betweenthe radially outer end of said inner reinforcing layer (7) and theradially outer end of said outer reinforcing layer (6), is higher thanor equal to 4 mm, preferably of from 5 mm to 8 mm.

In the particular embodiment of FIG. 6, the radially outer end of saidouter reinforcing layer (6) is staggered radially inward with respect tothe radially outer end of said inner reinforcing layer (7).

In the particular embodiment of FIG. 6, the radial distance (d5) betweenthe radially outer end of said inner reinforcing layer (7) and theradially outer end of said chafer (8), is lower than or equal to 35%,preferably of from 15% to 30%, with respect to a tire height (h2) incorrespondence to the maximum tire section width (W).

In the particular embodiment of FIG. 6, the radial distance (d6) betweenthe radially outer end of said outer reinforcing layer (6) and theradially outer end of said carcass ply turned up end portion (2 a), ishigher than or equal to 4 mm, preferably of from 5 mm to 8 mm.

In the particular embodiment of FIG. 6, the radially outer end of saidinner reinforcing layer (7), is placed at a tire height (h3) which islower than or equal to 60%, preferably of from 30% to 50%, morepreferably of from 35% to 45%, with respect to a tire height (h2) incorrespondence to the maximum tire section width (W).

1-29. (canceled)
 30. A tire comprising: a pair of bead structures, saidbead structures comprising at least one bead core and at least one beadfiller; a carcass structure having a substantially toroidal shapecomprising at least one carcass ply extending between said bead cores,the end portions of said carcass ply being turned up around said beadcores from the axially inner side to the axially outer side of saidtire; a belt structure applied in a radially external position withrespect to said carcass structure; a tread band radially superimposed onsaid belt structure; a pair of sidewalls, each sidewall being appliedlaterally on opposite sides with respect to said carcass structure; atleast one chafer placed axially outside with respect to said carcass plyturned up end portions; and at least two reinforcing layers placedaxially inside with respect to said carcass ply turned up end portions,said at least two reinforcing layers comprising: an outer reinforcinglayer provided with reinforcing elements parallel to each other andinclined with respect to the radial direction of said tire; and an innerreinforcing layer, placed axially inside with respect to said outerreinforcing layer, provided with reinforcing elements parallel to eachother and inclined with respect to the radial direction of said tire ina direction opposite to those of said outer reinforcing layer, wherein alowest radially inner end of one of said outer reinforcing layer andsaid inner reinforcing layer, is placed at a tire height which is lowerthan or equal to 35% with respect to a tire height in correspondencewith maximum tire section width.
 31. The tire according to claim 30,wherein the lowest radially inner end of one of said outer reinforcinglayer and said inner reinforcing layer, is placed at a tire height whichis 10% to 30% with respect to a tire height in correspondence with themaximum tire section width.
 32. The tire according to claim 31, whereinthe lowest radially inner end of one of said outer reinforcing layer andsaid inner reinforcing layer, is placed at a tire height which is 15% to25% with respect to a tire height in correspondence with the maximumtire section width.
 33. The tire according to claim 30, wherein a radialdistance between radially inner ends of said outer reinforcing layer andinner reinforcing layer, is higher than or equal to 4 mm.
 34. The tireaccording to claim 33, wherein the radial distance between the radiallyinner ends of said outer reinforcing layer and inner reinforcing layer,is 5 mm to 8 mm.
 35. The tire according to claim 30, wherein a radiallyinner end of said outer reinforcing layer is staggered radially outwardwith respect to a radially inner end of said inner reinforcing layer.36. The tire according to claim 30, wherein a radial distance between aradially outer end of said carcass ply turned up end portions and ahighest radially inner end of one of said outer reinforcing layer andsaid inner reinforcing layer, is higher than or equal to 8 mm.
 37. Thetire according to claim 36, wherein the radial distance between theradially outer end of said carcass ply turned up end portions and thehighest radially inner end of one of said outer reinforcing layer andsaid inner reinforcing layer, is 10 mm to 15 mm.
 38. The tire accordingto claim 30, wherein, when a radially outer end of said at least onechafer is placed at a higher height with respect to a radially outer endof said carcass ply turned up end portions, a radial distance between alowest radially outer end of one of said outer reinforcing layer andsaid inner reinforcing layer and the radially outer end of said at leastone chafer, is higher than or equal to 4 mm.
 39. The tire according toclaim 38, wherein the radial distance between the lowest radially outerend of one of said outer reinforcing layer and said inner reinforcinglayer and the radially outer end of said at least one chafer, is 5 mm to8 mm.
 40. The tire according to claim 30, wherein, when a radially outerend of said at least one chafer is placed at a lower height with respectto a radially outer end of said carcass ply turned up end portions, aradial distance between a lowest radially outer end of one of said outerreinforcing layer and said inner reinforcing layer and the radiallyouter end of said carcass ply turned up end portions, is higher than orequal to 4 mm.
 41. The tire according to claim 40, wherein the radialdistance between the lowest radially outer end of one of said outerreinforcing layer and said inner reinforcing layer and the radiallyouter end of said carcass ply turned up portions, is 5 mm to 8 mm. 42.The tire according to claim 30, wherein a radial distance betweenradially outer ends of said outer reinforcing layer and innerreinforcing layer, is higher than or equal to 4 mm.
 43. The tireaccording to claim 42, wherein the radial distance between the radiallyouter ends of said outer reinforcing layer and inner reinforcing layer,is 5 mm to 8 mm.
 44. The tire according to claim 30, wherein a radiallyouter end of said inner reinforcing layer is staggered radially outwardwith respect to a radially outer end of said outer reinforcing layer.45. The tire according to claim 30, wherein a radial distance between ahighest radially outer end of one of said outer reinforcing layer andsaid inner reinforcing layer and a radially outer end of said at leastone chafer, is lower than or equal to 35% with respect to a tire heightin correspondence with the maximum tire section width.
 46. The tireaccording to claim 45, wherein the radial distance between the highestradially outer end of one of said outer reinforcing layer and said innerreinforcing layer and the radially outer end of said at least onechafer, is 15% to 20% with respect to a tire height in correspondencewith the maximum tire section width.
 47. The tire according to claim 30,wherein a highest radially outer end of one of said outer reinforcinglayer and said inner reinforcing layer, is placed at a tire height whichis lower than or equal to 60% with respect to a tire height incorrespondence with a maximum tire section width.
 48. The tire accordingto claim 47, wherein the highest radially outer end of one of said outerreinforcing layer and said inner reinforcing layer, is placed at a tireheight which is 35% to 45% with respect to a tire height incorrespondence with the maximum tire section width.
 49. The tireaccording to claim 30, wherein the reinforcing elements of said outerreinforcing layer and said inner reinforcing layer are metal cords. 50.The tire according to claim 49, wherein said metal cords are steelcords.
 51. The tire according to claim 49, wherein said metal cordscomprise at least one elementary metal wire.
 52. The tire according toclaim 49, wherein said metal cords comprise at least one preformedelementary metal wire, and any remaining elementary metal wires are ofthe non-preformed type.
 53. The tire according to claim 49, wherein saidmetal cords are all preformed elementary metal wires.
 54. The tireaccording to claim 51, wherein said elementary metal wire has a diameterof 0.05 mm to 0.25 mm.
 55. The tire according to claim 30, wherein thereinforcing elements of said outer reinforcing layer are inclined with aradial inclination angle of +10° to +35°.
 56. The tire according toclaim 55, wherein the reinforcing elements of said outer reinforcinglayer are inclined with a radial inclination angle of +15° to +25°. 57.The tire according to claim 30, wherein the reinforcing elements of saidinner reinforcing layer are inclined with a radial inclination angle of−10° to −35°.
 58. The tire according to claim 57, wherein thereinforcing elements of said inner reinforcing layer are inclined with aradial inclination angle of −15° to −25°.